Forty years ago, the Supreme Court decided that police do not need a warrant to look through anything a person is carrying when arrested. But that was long before smartphones gave people the ability to take with them the equivalent of millions of documents and thousands of photos. The justices are being asked to resolve a new clash of technology and privacy in the digital age.

Washington — The US Supreme Court agreed Friday to examine whether police are free to conduct a warrantless search of the digital contents of a cellphone being carried by someone they arrest.

The Fourth Amendment generally requires police to obtain a judicially authorized warrant before searching a suspect, his house, papers, or effects. But the Supreme Court has carved out exceptions – including one that permits police to inspect the contents of a closed container police find during the arrest and search of a person.

The question before the court is whether police examining the contents of a cellphone is the same – for the purposes of Fourth Amendment privacy protections – as looking inside a container found in an arrestee’s pocket.

One involves an alleged crack cocaine dealer in Boston named Brima Wurie, who police say used a cellphone to coordinate narcotics deals from his car. Police used data in the phone to identify the location of a suspected drug stash house.

The other case involves a suspected gang member in Los Angeles, David Leon Riley, whose cellphone contained text entries and photos that helped police link Mr. Riley to an earlier gang-related shooting.

In both cases, the police used information stored on the seized cellphone as evidence to help build a criminal case against the suspect. They collected the information and used it as evidence without first obtaining a warrant.

Lawyers for the accused men argue that the Fourth Amendment ban on unreasonable searches and seizures bars police from examining the content of a cellphone without first obtaining a warrant.

They say the general rule that police can open a closed container discovered during the bodily search of a suspect should not be extended to permit warrantless searches of cellphones.

Such searches conducted at the time of arrest are performed to help police identify any weapons held by the suspect. They are also performed to prevent the destruction of any evidence of a crime.

Once a cellphone is seized, defense lawyers say, there are no exigent circumstances or other reasons justifying a search without first obtaining a warrant.

Law enforcement officials counter that data on a cellphone could be accessed remotely and destroyed by a third party after others learned of the arrest. They want a bright-line rule that would allow police to examine anything they find in a person’s pockets without having to justify the intrusion to a neutral judge.

Defense lawyers say that enormous advances in cellphone technology have converted telephones into repositories of massive amounts of personal information. That should make a difference, they say, in whether police need a warrant before they begin exploring the contents of someone’s personal files accessible via the cellphone.

Examining the stored data in a smart phone is far different than opening a crumpled cigarette carton found in a suspect’s pocket, they argue.

“While physical containers face obvious space-related constraints, cellphones are capable of storing a virtually limitless amount of information in a single, compact device,” wrote Stanford Law School Professor Jeffrey Fisher in his brief urging the high court to take up the Riley case.

So-called “smart phones” are designed to store and quickly display information about every aspect of a person’s life, from bank statements and frequent contacts, to personal photos, to years’ worth of archived text and e-mail messages.

“A search incident to arrest could, at the touch of a button, become a search of private and confidential information such as medical records, banking activity, and work-related emails,” Professor Fisher said.

“The contents of a person’s cellphone can also contain intimate details and video of people’s private lives, potentially exposing them to extreme embarrassment or worse,” Fisher wrote.

Lawyers with the California Attorney General’s office counter that seized cellphones are a permissible way to collect evidence.

“This case involves a straightforward application of bedrock Fourth Amendment principles,” Deputy Attorney General Christine Bergman wrote in her brief urging the justices to reject the Riley case.

She downplayed the importance of the information gained by police from the phone as “merely trivial.” But Ms. Bergman acknowledged that the information helped prosecutors obtain a longer sentence in the case.

Information from the cellphone helped police show Riley was a gang member – evidence that boosted his potential time in prison. Instead of a seven-year sentence, he was subject to a sentence of 15 years to life.

Bergman dismissed claims that a warrantless search of a smart phone would allow police access to important and intimate details of a person’s life.

“There is no evidence concerning whether the officers accessed any information on the cellphone such as appointment calendars, e-mail correspondence, internet-related activity, or applications,” she said.

“Based on the record, the search involved no intrusion greater than the viewing of the photographs, video, and text entries on the cellphone,” she said. “The record does not support petitioner’s portrayal of an unfettered search through a wide range of information disclosing petitioner’s personal and private affairs.”

The issue has created a split among federal appeals courts and state supreme courts. The First US Circuit Court of Appeals in Boston ruled that the cellphone search in the Wurie case violated the Fourth Amendment. The supreme courts of Ohio and Florida have reached the same conclusion.

In contrast, the Fourth, Fifth, and Seventh Circuits and the supreme courts in Massachusetts, Georgia, and California have ruled that cellphone searches do not violate the Fourth Amendment.

The cases are US v. Brima Wurie (13-212), and David Riley v. California (13-132).